Bearing arrangement and a bearing cage

ABSTRACT

A bearing arrangement comprises a rolling element bearing assembly including a bearing cage. The bearing cage comprises an annular cage body having an inner surface defining a coaxial bore. The bearing cage has a plurality of circumferentially spaced pockets and each pocket houses a rotatable rolling element. A first annular skirt extends axially from a radially inner end of a first axial end of the cage body and at least one first support member extends radially and axially from the remote axial end of the first annular skirt to the radially outer end of annular cage body. The bearing cage is hollow and has a high stiffness to weight ratio. The bearing arrangement is particularly suitable for use for a planet gear of a planetary gearbox. The planetary gearbox may be for a gas turbine engine.

The present disclosure concerns a rolling element bearing and inparticular to a rolling element bearing cage. The present disclosureconcerns a roller bearing or a ball bearing, and in particular concernsa roller bearing cage or a ball bearing cage. The present disclosure ismore particularly concerned with rolling element bearings for aplanetary gearbox.

The bearing cage of a rolling element bearing controls the position ofthe rolling elements to avoid neighbouring rolling elements contactingand damaging each other. A bearing cage must have suitable strength andrigidity and must have a minimum weight. These attributes are ofparticular concern in the case of roller bearings used for the planetgears of high speed planetary gearboxes. The loads imparted due torotation are potentially very large and therefore a reduction in themass of the bearing cage reduces the loads experienced by the bearingcage. A loss of rigidity of the bearing cage may compromise the bearingcage pilot load bearing capacity producing wear and reliabilityproblems.

A conventional bearing cage designed for high pilot loads has wide pilotlands, or skirts, extending axially from the cage body to support a widefilm of lubricant, oil, with a high load capacity. The bearing cage isessentially a solid ring and it is difficult to provide adequatestiffness across the full axial width of the skirts and cage bodywithout adding excessive levels of mass, which increases the loadsfurther. The solid bearing cage has a relatively low stiffness to weightratio which may result in bending of the skirts due to journal filmloads and/or bending of the cage due to the applied loads.

A conventional bearing cage with a relatively low stiffness to massratio compromises the ability to provide adequate pilot land journalcapacity, e.g. provide skirts with adequate axial length. If a uniformlystiff bearing cage is provided the mass of the bearing cage is too highresulting in increased loading. If a relatively light weight bearingcage is provided there is a compromise in the alignment of the journalbearing surfaces, which also reduces the load bearing capacity. Thesefactors are particularly important in bearing cages for planet gears ofhigh speed planetary gearboxes, which are subjected to high lateralaccelerations.

Accordingly the present disclosure seeks to provide a bearing cage and abearing arrangement which reduces, or overcomes, the above mentionedproblems.

According to a first aspect of the invention there is provided a rollingelement bearing cage, the rolling element bearing cage comprising anannular cage body having an inner surface defining a coaxial bore, thebearing cage having a plurality of circumferentially spaced pockets,each pocket housing a rotatable rolling element, a first annular skirtextending axially from a radially inner end of a first axial end of thecage body and at least one first support member extending radially andaxially from the remote axial end of the first annular skirt to theradially outer end of annular cage body.

According to a second aspect of the invention there is provided abearing arrangement comprising a rolling element bearing assemblyincluding a bearing cage, the bearing cage comprising an annular cagebody having an inner surface defining a coaxial bore, the bearing cagehaving a plurality of circumferentially spaced pockets, each pockethousing a rotatable rolling element, a first annular skirt extendingaxially from a radially inner end of a first axial end of the cage bodyand at least one first support member extending radially and axiallyfrom the remote axial end of the first annular skirt to the radiallyouter end of annular cage body.

The at least one first support member may be annular such that a firstannular chamber is defined by the annular cage body, the first annularskirt and the first annular support member.

The first annular chamber may contain a low density filler. The lowdensity filler may comprise a foam. The foam may be a metallic foam.

The at least one first support member may comprise a plurality ofmembers.

A second annular skirt may extend axially from the radially inner end ofa second axial end of the cage body arid at least one second supportmember extending radially and axially from the remote axial end of thesecond annular skirt to the radially outer end of annular cage body.

The at least one second support member may be annular such that a secondannular chamber is defined by the annular cage body, the second annularskirt and the second annular support member.

The second annular chamber may contain a low density filler. The lowdensity filler may comprise a foam. The foam may be a metallic foam.

The at least one second support member may comprise a plurality ofmembers.

The cage body, the first annular skirt and the at least one firstsupport member may be a monolithic structure. The cage body, the firstannular skirt, the at least one first support member and the foam in thefirst annular chamber may be a monolithic structure. The cage body, thefirst annular skirt, the at least one first support member, the secondannular skirt and the at least one second support member may be amonolithic structure. The cage body, the first annular skirt, the atleast one first support member, the foam in the first annular chamber,the second annular skirt, the at least one second support member and thefoam in the second annular chamber may be a monolithic structure. Themonolithic structure may be produced by additive layer manufacture, e.g.direct laser deposition, laser powder bed, selective laser sinteringetc.

The rolling elements may be roller bearings or ball bearings.

The bearing arrangement may be arranged between a shaft and a statorstructure. The bearing arrangement may be arranged between a first shaftand a second shaft. The bearing arrangement may be arranged between aplanet gear and a planet gear carrier of a planetary gearboxarrangement. The bearing arrangement may be arranged between a star gearand a star gear carrier of a star gearbox arrangement.

The bearing arrangement may be a bearing arrangement for a gas turbineengine, a turbomachine, a steam turbine or an internal combustionengine.

The skilled person will appreciate that except where mutually exclusive,a feature described in relation to any one of the above aspects of theinvention may be applied mutatis mutandis to any other aspect of theinvention.

Embodiments of the invention will now be described by way of exampleonly, with reference to the figures, in which:

FIG. 1 is a part sectional side view of a geared turbofan gas turbineengine having a bearing arrangement according to the present disclosure.

FIG. 2 is an enlarged part sectional side view of a portion of thegeared turbofan gas turbine engine shown in FIG. 1.

FIG. 3 is an enlarged cross-sectional view though the gearbox shown inFIG. 2 having a bearing arrangement according to the present disclosure.

FIG. 4 is a further enlarged cross-sectional view through a bearingarrangement according to the present disclosure.

FIG. 5 is a further enlarged cross-sectional view through an alternativebearing arrangement according to the present disclosure.

FIG. 6 is a further enlarged cross-sectional view through a furtherbearing arrangement according to the present disclosure.

FIG. 7 is a further enlarged cross-sectional view through anotherbearing arrangement according to the present disclosure.

FIG. 8 is a further enlarged cross-sectional view through anotherbearing arrangement according to the present disclosure.

FIG. 9 is an enlarged cross-sectional view through an alternativegearbox having a bearing arrangement according to the presentdisclosure.

FIG. 10 is an enlarged cross-sectional view through a further gearboxhaving a bearing arrangement according to the present disclosure.

With reference to FIGS. 1 and 2, a geared turbofan gas turbine engine isgenerally indicated at 10, having a principal and rotational axis 9. Theengine 10 comprises, in axial flow series, an air intake 12, apropulsive fan 13, an intermediate-pressure, or booster, compressor 14,a high-pressure compressor 15, combustion equipment 16, a high-pressureturbine 17, a low-pressure turbine 19 and a core exhaust nozzle 20. Theintermediate-pressure compressor 14, the high-pressure compressor 15,the combustion equipment 16, the high-pressure turbine 17 and thelow-pressure turbine 19 form a core engine 11. A nacelle 21 generallysurrounds the engine 10 and defines the intake 12, a bypass duct 22 anda bypass exhaust nozzle 18.

The gas turbine engine 10 works in the conventional manner so that airentering the intake 12 is accelerated by the fan 13 to produce two airflows: a first air flow A into the intermediate-pressure compressor 14and a second air flow B which passes through the bypass duct 22 toprovide the majority of the propulsive thrust. The intermediate-pressurecompressor 14 compresses the air flow directed into it before deliveringthat air to the high-pressure compressor 15 where further compressiontakes place.

The compressed air exhausted from the high-pressure compressor 15 isdirected into the combustion equipment 16 where it is mixed with fueland the mixture combusted. The resultant hot combustion products thenexpand through, and thereby drive the high and low-pressure turbines 17,19 before being exhausted through the core nozzle 20 to provideadditional propulsive thrust. The high-pressure turbine 17 drives thehigh-pressure compressor 15 by a shaft 23. The low-pressure turbine 19drives the intermediate-pressure compressor 14 directly via shafts 26and 27. The low-pressure turbine 19 drives the fan 13 indirectly via theshaft 26, a gearbox 28 and a shaft 38. The gearbox 28 comprises a sungear 30, an annulus gear 32, a plurality of planet gears 34 and a planetgear carrier 36. The sun gear 30 meshes with the planet gears 34 and theplanet gears 32 mesh with the annulus gear 32. The planet gear carrier36 constrains the planet gears 34 to precess around the sun gear 30 insynchronicity whilst enabling each planet gear 34 to rotate about itsown axis independently. The planet gear carrier 36 is coupled via theshaft 38 to the fan 13 in order to drive its rotation about the engineaxis 9. The annulus gear 32 is coupled to a static structure 24. Theaxes of the planet gears 34 and the axis of the planet gear carrier 36are parallel to the engine axis 9.

The gearbox 28 is shown more clearly in FIG. 3 and the planet gearcarrier 36 comprises a first ring 36A, a second ring 36B spaced axiallyfrom the first ring 36A and a plurality of circumferentially spacedaxles 40 which extend axially between the first ring 36A and the secondring 36B. Each planet gear 34 is rotatably mounted on a respective oneof the axles 40 and an annular extension, e.g. an extension shaft, 36Cextends axially from the first ring 36A. Each planet gear 34 isrotatably mounted in the planet gear carrier 36 by at least one planetgear bearing 42. The extension shaft 36C is rotatably mounted in thestatic structure 24 by a roller bearing 44, the shaft 38 is rotatablymounted in the static structure 24 by a ball bearing 45 and a rollerbearing 46 axially spaced from the ball bearing 45. The shaft 26 isrotatably mounted in further static structure 25 by a ball bearing 47.

In this particular embodiment each planet gear 34 is rotatably mountedon the planer gear carrier 36 by two roller bearings 42. The planet gearbearings 42 of the gearbox arrangement 28 of FIG. 3 may be provided witha bearing cage as described with reference to FIG. 4, 5, 6 or 7.

A bearing arrangement according to the present disclosure is shown moreclearly in FIG. 4. The bearing arrangement 42 comprises a rollingelement bearing assembly including a bearing cage 50, the bearing cage50 comprises an annular cage body 52 having an inner surface 54 defininga coaxial bore, the bearing cage 50 having a plurality ofcircumferentially spaced pockets 56 and each pocket 56 housing arotatable rolling element 58. A first annular skirt 60 extends axiallyfrom a radially inner end 64 of a first axial end 62 of the cage body 52and at least one first support member 66 extends radially and axiallyfrom the remote axial end 68 of the first annular skirt 60 to theradially outer end 70 of the first axial end 62 of the annular cage body52. A second annular skirt 72 extends axially from the radially innerend 76 of a second axial end 74 of the cage body 52 and at least onesecond support member 78 extends radially and axially from the remoteaxial end 80 of the second annular skirt 72 to the radially outer end 82of the second axial end 74 of the annular cage body 52. The rollingelements 58 and the bearing cage 50 are positioned radially between aninner race 59 and an outer race 61 and the rolling elements 58 arerollers.

The at least one first support member 66 is annular such that a firstannular chamber 84 is defined by the annular cage body 52, the firstannular skirt 60 and the first annular support member 66. In thisexample the first annular chamber 84 is empty. Similarly, the at leastone second support member 78 is annular such that a second annularchamber 86 is defined by the annular cage body 52, the second annularskirt 72 and the second annular support member 78 and the second annularchamber 86 is empty.

Thus, it clear that the annular cage body 52, the first annular skirt60, the first annular support member 66, the second annular skirt 72 andthe second annular support member 78 together form a hollow bearing cage50 with two annular chambers 84 and 86. This hollow bearing cage 50 hasa high stiffness to weight ratio. The first and second annular supportmembers 66 and 78 form a structural skin which utilises material moreeffectively against bending deflections which reduce the cage pilotjournal bearing capacity of the first and second annular skirts ofconventional bearing cage designs. The bearing cage 50 may be tuned toprovide a favourable distortion behaviour across the pilot land areas,e.g. across the axial length of the first and second annular skirts 60and 72. The bearing cage 50 is particularly useful for a rolling elementbearing which experiences very high lateral accelerations such asrolling element bearings used for planet gears in a planetary gearbox inwhich case the inner race 59 is provided on the axle 40 and the outerrace 61 is provided on the planet gear 34. The bearing cage may also beused in conventional rolling element bearings in which a high stiffnessto mass ratio may alleviate cage dynamics issues or simply to reduce theweight of the bearing cage.

In this example the cage body 52, the first annular skirt 60, the atleast one first annular support member 66, the second annular skirt 72and the at least one second annular support member 78 is a monolithicstructure, e.g. an integral structure or one piece structure. Inparticular both of the ends of the first and second annular supportmembers 66 and 78 are integral with the remote axial ends 68 and 80 ofthe first and second annular skirts 60 and 72 and also with the radiallyouter ends 70 and 82 of the first and second axial ends 62 and 74 of theannular cage body 52. The monolithic structure may be produced byadditive layer manufacture, e.g. direct laser deposition, laser powderbed, selective laser sintering etc.

A further bearing arrangement according to the present disclosure isshown more clearly in FIG. 5. The bearing arrangement 42A shown in FIG.5 is substantially the same as that shown in FIG. 4, and like parts aredenoted by like numerals. FIG. 5 differs in that the first and secondannular chambers 84 and 86 contain a low density filler 88and 90respectively. The low density filler 88 and 90 comprises a foam, forexample a metallic foam.

In this example the cage body 52, the first annular skirt 60, the atleast one first annular support member 66, the foam 88 in the firstannular chamber 64, the second annular skirt 72, the at least one secondannular support member 78 and the foam 90 in the second annular chamber86 is a monolithic structure, e.g. an integral structure or one piecestructure. The monolithic structure may be produced by additive layermanufacture, e.g. direct laser deposition, laser powder bed, selectivelaser sintering etc.

A further bearing arrangement according to the present disclosure isshown more clearly in FIG. 6. The bearing arrangement 42B shown in FIG.6 is substantially the same as that shown in FIG. 4, and like parts aredenoted by like numerals. FIG. 6 differs in that the radially outer ends67 and 79 of the first and second annular support members 66 and 78respectively are not integrally attached to the radially outer ends 70and 82 of the first and second axial ends 62 and 74 respectively of theannular cage body 52. In this example the radially outer ends 67 and 79of the first and second annular support members 66 and 78 respectivelyare located radially underneath the radially outer ends 70 and 82 of thefirst and second axial ends 62 and 74 respectively of the annular cagebody 52.

The first annular skirt 60 and the first annular support 66 are formedfrom a single piece and the first annular support 66 is rolled over orupset to its final position. Similarly, the second annular skirt 672 andthe second annular support 78 are formed from a single piece and thesecond annular support 78 is rolled over or upset to its final position.The radially outer ends 67 and 79 of the first and second annularsupport members 66 and 78 may be welded, or brazed or bonded to theradially outer ends 70 and 82 of the first and second axial ends 62 and74 respectively of the annular cage body 52.

Another bearing arrangement according to the present disclosure is shownmore clearly in FIG. 7. The bearing arrangement 42C shown in FIG. 7 issubstantially the same as that shown in FIG. 4, and like parts aredenoted by like numerals. FIG. 7 differs in that the radially outer ends67 and 79 of the first and second annular support members 66 and 78respectively are welded, or brazed or bonded to the radially outer ends70 and 82 of the first and second axial ends 62 and 74 respectively ofthe annular cage body 52. Similarly, the radially inner ends 65 and 77of the first and second annular support members 66 and 78 respectivelyare welded, or brazed or bonded to the remote axial ends 68 and 80 ofthe first and second annular skirts 60 and 72 respectively.

Another bearing arrangement according to the present disclosure is shownmore clearly in FIG. 8. The bearing arrangement 42D shown in FIG. 8 issubstantially the same as that shown in FIG. 4, and like parts aredenoted by like numerals. FIG. 8 differs in that the rolling elements 58are balls.

FIG. 9 shows an arrangement in which the low-pressure turbine 19 drivesthe fan 13 indirectly via the shaft 126, a gearbox 128 and a shaft 138.The gearbox 128 comprises a sun gear 130, an annulus gear 132, aplurality of star gears 134 and a star gear carrier 136. The sun gear130 meshes with the star gears 134 and the star gears 134 mesh with theannulus gear 132. The star gear carrier 136 enabling each star gear 134to rotate about its own axis independently. The star gear carrier 136 iscoupled to a static structure 124. The annulus gear 132 is coupled viathe shaft 138 to the fan 13 in order to drive its rotation about theengine axis 9. The axes of the star gears 134 are parallel to the engineaxis 9. The star gear carrier 136 comprises a first ring 136A, a secondring 136B spaced axially from the first ring 136A and a plurality ofcircumferentially spaced axles 140 which extend axially between thefirst ring 136A and the second ring 136B. Each star gear 134 isrotatably mounted on a respective one of the axles 140 and an annularextension 136C extends axially from the first ring 136A. Each star gear134 is rotatably mounted in the star gear carrier 136 by at least oneplanet gear bearing 142. The annular extension 1360 is secured to thestatic structure 124. In this particular embodiment each star gear 134is rotatably mounted on the star gear carrier 136 by two roller bearings142. The star gear bearings 142 of the gearbox arrangement 128 of FIG. 9may be provided with a bearing cage as described with reference to FIG.4, 5, 6 or 7.

FIG. 10 shows an arrangement in which the low-pressure turbine 19 drivestwo fans indirectly via the shaft 226, a gearbox 228 and shaft 238A and238B. The gearbox 228 comprises a sun gear 230, an annulus gear 232, aplurality of planet gears 234 and a planet gear carrier 236. The sungear 230 meshes with the planet gears 234 and the planet gears 234 meshwith the annulus gear 232. The planet gear carrier 236 enabling eachplanet gear 234 to rotate about its own axis independently. The planetgear carrier 236 is coupled via the shaft 238A to a first propulsor (notshown) and the annulus gear 232 is coupled via the shaft 238B to asecond propulsor (not shown) in order to drive their rotation about theengine axis 9. The propulsors are driven to rotate in oppositerotational directions. The axes of the planet gears 234 are parallel tothe engine axis 9. The planet gear carrier 236 comprises a first ring236A, a second ring 236B spaced axially from the first ring 236A and aplurality of circumferentially spaced axles 240 which extend axiallybetween the first ring 236A and the second ring 236B. Each planet gear234 is rotatably mounted on a respective one of the axles 240 and anannular extension 236C extends axially from the first ring 236A. Eachplanet gear 234 is rotatably mounted in the planet gear carrier 236 byat least one planet gear bearing 242. The annular extension 236C isrotatably mounted in the static structure 224 by a bearing 244. In thisparticular embodiment each planet gear 234 is rotatably mounted on theplanet gear carrier 236 by two roller bearings. The planet gear bearings242 of the gearbox arrangement 228 of FIG. 10 may be provided with abearing cage as described with reference to FIG. 4, 5, 6 or 7.

Although the present disclosure has been described with reference to theuse of a bearing arrangement for a planet gear or star gear it may alsobe used for example for a bearing arrangement between a shaft and staticstructure for example the roller bearing 45 between the shaft 36C andthe static structure 24 in FIG. 3 and/or the roller bearing 46 and/orthe ball bearing 45 between the shaft 38 and the static structure 24 inFIG. 1 and/or for the ball bearing 47 between the shaft 26 and thestatic structure 25 of FIG. 1.

Although the present disclosure has been described with reference to asingle first annular support member and a single annular second supportmember it may be possible to provide a plurality of circumferentiallyspaced first support members and/or a plurality of circumferentiallyspaced second support members.

Although the present disclosure has been described with reference tofirst and second annular skirts and at least one first support memberand at least one second support member on the bearing cage it may bepossible to provide only a single annular skirt and at least one firstsupport member on the bearing cage.

The rolling elements may be roller bearings or ball bearings.

The bearing arrangement may be arranged between a shaft and a statorstructure. The bearing arrangement may be arranged between a first shaftand a second shaft. The bearing arrangement may be arranged between aplanetary gear and a planetary gear carrier of a planetary gearboxarrangement. The bearing arrangement may be arranged between a star gearand a star gear carrier of a star gearbox arrangement.

The bearing arrangement may be a bearing arrangement for a gas turbineengine, a turbomachine, a steam turbine or an internal combustionengine.

In each of the arrangements described above the sun gear, the annulusgear, the planet gear carrier, or star gear carrier, and the shaft arecoaxial.

As described above, the gas turbine engine comprises a propulsor, anintermediate-pressure compressor, a high-pressure compressor, ahigh-pressure turbine and a low-pressure turbine, the high-pressureturbine is arranged to directly drive the high-pressure compressor, thelow-pressure turbine is arranged to directly drive theintermediate-pressure compressor and the low-pressure turbine isarranged to drive the propulsor via a gearbox.

Alternatively, the gas turbine engine comprises a propulsor, anintermediate-pressure compressor, a high-pressure compressor, ahigh-pressure turbine and a low-pressure turbine, the high-pressureturbine is arranged to directly drive the high-pressure compressor, thelow-pressure turbine is arranged to directly drive the propulsor and thelow-pressure turbine is arranged to drive the intermediate-pressurecompressor via a gearbox.

Alternatively, the gas turbine engine comprises a propulsor, anintermediate-pressure compressor, a high-pressure compressor, ahigh-pressure turbine, an intermediate-pressure turbine and alow-pressure turbine, the high-pressure turbine is arranged to directlydrive the high-pressure compressor, the intermediate-pressure turbine isarranged to directly drive the intermediate- pressure compressor and thelow-pressure turbine is arranged to drive the propulsor via a gearbox.

Alternatively the gas turbine engine may comprise a propulsor, ahigh-pressure compressor, a high-pressure turbine and a low-pressureturbine, the high-pressure turbine is arranged to directly drive thehigh-pressure compressor and the low-pressure turbine is arranged todrive the propulsor via a gearbox.

Alternatively, the gas turbine engine comprises a first propulsor, asecond propulsor, an intermediate-pressure compressor, a high-pressurecompressor, a high-pressure turbine, an intermediate-pressure turbineand a low-pressure turbine, the high-pressure turbine is arranged todirectly drive the high-pressure compressor, the intermediate-pressureturbine is arranged to directly drive the intermediate-pressurecompressor and the low-pressure turbine is arranged to drive the firstpropulsor and the second propulsor via a gearbox.

Alternatively, the gas turbine engine comprises a first propulsor, asecond propulsor, a low-pressure compressor, a high-pressure compressor,a high-pressure turbine, a low-pressure turbine and a free powerturbine, the high-pressure turbine is arranged to directly drive thehigh-pressure compressor, the low-pressure turbine is arranged todirectly drive the low-pressure compressor and the free power turbine isarranged to drive the first propulsor and the second propulsor via agearbox.

Alternatively, the gas turbine engine comprises a first propulsor, asecond propulsor, a low-pressure compressor, a high-pressure compressor,a high-pressure turbine and a low-pressure turbine, the high-pressureturbine is arranged to directly drive the high-pressure compressor, thelow-pressure turbine is arranged to directly drive the low-pressurecompressor and the low-pressure turbine is arranged to drive the firstpropulsor and the second propulsor via a gearbox.

The sun gear may be driven by a low-pressure turbine, the annulus gearmay be secured to static structure and the planet gear carrier may bearranged to drive a propulsor.

The sun gear may be driven by the low-pressure turbine, the planet gearcarrier may be secured to static structure and the annulus gear may bearranged to drive a propulsor. In this arrangement the planet gears aretermed star gears and the annular extension of the planet gear carrieris secured to the static structure. In this arrangement each planet gearrotates about its own axis and the planet gear carrier does not rotateabout the engine axis. The axes of the planet gears are parallel to theengine axis.

The planet gear carrier may be driven by the low-pressure turbine, thesun gear may be secured to static structure and the annulus gear may bearranged to drive a propulsor.

The sun gear may be driven by the low-pressure turbine, the planet gearcarrier may be arranged to drive a first propulsor and the annulus gearmay be arranged to drive a second propulsor.

The propulsor may be a fan or a propeller.

It will be understood that the invention is not limited to theembodiments above-described and various modifications and improvementscan be made without departing from the concepts described herein. Exceptwhere mutually exclusive, any of the features may be employed separatelyor in combination with any other features and the disclosure extends toand includes all combinations and sub-combinations of one or morefeatures described herein.

The project leading to this application has received funding from theClean Sky 2 Joint Undertaking under the European Union's Horizon 2020research and innovation programme under grant reference No.CS2-ENG-GAM-2014-2015-01.

1. A bearing arrangement comprising a rolling element bearing assembly including a bearing cage, the bearing cage comprising an annular cage body having an inner surface defining a coaxial bore, the bearing cage having a plurality of circumferentially spaced pockets, each pocket housing a rotatable rolling element, a first annular skirt extending axially from a radially inner end of a first axial end of the cage body and at least one first support member extending radially and axially from the remote axial end of the first annular skirt to the radially outer end of annular cage body.
 2. A bearing arrangement as claimed in claim 1 wherein the at least one first support member is annular such that a first annular chamber is defined by the annular cage body, the first annular skirt and the first annular support member.
 3. A bearing arrangement as claimed in claim 2 wherein the cage body, the first annular skirt and the at least one first support member is a monolithic structure.
 4. A bearing arrangement as claimed in claim 2 wherein the first annular chamber contains a low density filler.
 5. A bearing arrangement as claimed in claim 4 wherein the low density filler comprises a foam.
 6. A bearing arrangement as claimed in claim 5 wherein the cage body, the first annular skirt, the at least one first support member and the foam in the first annular chamber is a monolithic structure.
 7. A bearing arrangement as claimed in claim 1 wherein a second annular skirt extends axially from the radially inner end of a second axial end of the cage body and at least one second support member extending radially and axially from the remote axial end of the second annular skirt to the radially outer end of annular cage body.
 8. A bearing arrangement as claimed in claim 7 wherein the at least one second support member is annular such that a second annular chamber is defined by the annular cage body, the second annular skirt and the second annular support member.
 9. A bearing arrangement as claimed in claim 8 wherein the cage body, the first annular skirt, the at least one first support member, the second annular skirt and the at least one second support member is a monolithic structure.
 10. A bearing arrangement as claimed in claim 8 wherein the second annular chamber contains a low density filler.
 11. A bearing arrangement as claimed in claim 10 wherein the low density filler comprises a foam.
 12. A bearing arrangement as claimed in claim 11 wherein the cage body, the first annular skirt, the at least one first support member, the foam in the first annular chamber, the second annular skirt, the at least one second support member and the foam in the second annular chamber is a monolithic structure.
 13. A bearing arrangement as claimed in claim 3 wherein the monolithic structure is produced by additive layer manufacture.
 14. A bearing arrangement as claimed in claim 13 wherein the monolithic structure is produced by a method selected from the group consisting of direct laser deposition, laser powder bed and selective laser sintering.
 15. A bearing arrangement as claimed in claim 1 wherein the at least one first support member comprises a plurality of members.
 16. A bearing arrangement as claimed in claim 7 wherein the at least one second support member comprises a plurality of members.
 17. A bearing arrangement as claimed in claim 1 wherein the rolling elements are selected from the group consisting of roller bearings and ball bearings.
 18. A bearing arrangement as claimed in claim 1 wherein the bearing arrangement is arranged between a shaft and a further component, the further component is selected from the group consisting of a stator structure and a second shaft.
 19. A bearing arrangement as claimed in claim 1 wherein the bearing arrangement is arranged between a planet gear and a planet gear carrier of a planetary gearbox arrangement.
 20. A rolling element bearing cage, the rolling element bearing cage comprising an annular cage body having an inner surface defining a coaxial bore, the bearing cage having a plurality of circumferentially spaced pockets, each pocket housing a rotatable rolling element, a first annular skirt extending axially from a radially inner end of a first axial end of the cage body and at least one first support member extending radially and axially from the remote axial end of the first annular skirt to the radially outer end of annular cage body, 